Pd₃ and Pt₃ species on the α-Al₂O₃(0 0 0 1) surface: Cluster models embedded in an elastic polarizable environment

Adsorption of small metal particles Pd₃ and Pt₃ on an Al-terminated surface α-Al₂O₃(0 0 0 1) was studied by means of all-electron scalar relativistic density functional calculations. We employed stoichiometric model clusters and our recently developed embedding scheme which accurately accounts for the adsorption-induced substrate relaxation. We compared M₃ particles oriented parallel to and almost upright on the surface. The calculations show upright species which interact with two O anions and are stabilized by nearby Al cations to be most stable, with adsorption energies of 1.5 eV (Pd₃) and 2.6 eV (Pt₃). We also discuss the important role of substrate rearrangement.